The example is chosen to test the accuracy of the operator splitting method as described in Section . To compute the global error \(E\)  analogous to (REF ) we use always a half time step twice in the subproblem (REF ) when compared to the time step of subproblem (REF ) as described in Section . Consequently, the maximal Courant number in the \(x\)  direction is a half of the maximal Courant number in \(y\)  direction. Note that for explicit methods a typical stability restriction is given by the sum of directional Courant numbers that is required to be smaller than one [1]}.
We compute the example with the maximal Courant number in \(y\)  direction being \(1.6\) .
